diff --git a/dsv4/kernels/router/nvfp4_fused_router_kernel.py b/dsv4/kernels/router/nvfp4_fused_router_kernel.py
index 4efc965e..749db248 100644
--- a/dsv4/kernels/router/nvfp4_fused_router_kernel.py
+++ b/dsv4/kernels/router/nvfp4_fused_router_kernel.py
@@ -227,6 +227,10 @@ class Nvfp4FusedRouterKernel:
             self._setup_attributes()
             tiled_mma = self._tiled_mma
             tiled_mma_sfb = self._tiled_mma_sfb
+
+            # Ensure mma_tiler contains CuTe Ints (not Python ints)
+            self.mma_tiler = (cutlass.Int32(self.mma_tiler[0]), cutlass.Int32(self.mma_tiler[1]), cutlass.Int32(self.mma_tiler[2]))
+            self.mma_tiler_sfb = (cutlass.Int32(self.mma_tiler_sfb[0]), cutlass.Int32(self.mma_tiler_sfb[1]), cutlass.Int32(self.mma_tiler_sfb[2]))
             atom_thr_size = cute.size(tiled_mma.thr_id.shape)
 
             a_smem_0 = cute.slice_(self.a_smem_layout_staged, (None, None, None, 0))